Magazine article Science News

Taking Chlorine out of Tough Pollutants

Magazine article Science News

Taking Chlorine out of Tough Pollutants

Article excerpt

The crisp white paper that readers and writers enjoy bears more than a monetary price. The unseen cost comes in the form of pollution, since many of the chemicals generated in paper manufacturing resist natural degradation and instead tend to linger, unwanted, in the environment.

In the process of bleaching wood pulp to press out pearly reams, paper mills may create up to 250 different types of chlorinated contaminants (SN: 5/12/90, p.303). The most tenacious include a class of halogenated aromatic compounds called trichlorophenols (TCPs). At the heart of a TCP molecule lies a tightly bound ring of atoms that includes three chlorines.

The structure of TCPs allows them to stand up to nature's degradative forces, presenting soil-borne microorganisms with an indigestible meal. Their resistance to decomposition causes trouble for the paper industry, which must safely dispose of the long-lasting waste.

Offering a potential solution to this problem, chemists Alexander Sorokin and Bernard Meunier at the National Scientific Research Center (CNRS) in Toulouse Cedex, France, and Jean-Louis Seris of GRL-Biotechnology in Artix describe a new type of catalytic system for breaking up TCPs.

Using hydrogen peroxide, a relatively safe and environmentally benign agent, coupled with a readily available iron-based catalyst, the new system oxidizes TCP molecules by breaking open the chlorinated rings at their cores. The chemical compounds resulting from the reaction can then undergo natural degradation, the team reports in the May 26 Science.

"Many of these pollutants can be converted into less dangerous organic products and can be eventually degraded by different microorganisms," the researchers point out. "Systems that can remove halogen substitutents from [TCPs] may produce compounds that can be more easily biodegraded.

"In this case," they add, "the use of chemical catalysts to convert recalcitrant pollutants to more degradable molecules by microorganisms would be beneficial. …

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